1. Field of the Invention
The present invention relates to an attrition resistant catalyst for use in the ammoxidation of an unsaturated hydrocarbon to the corresponding unsaturated nitrile. In particular, the present invention is directed to an improved catalytic composition for the ammoxidation of propylene and/or isobutylene to acrylonitrile and/or methacrylonitrile, respectively.
2. Description of the Prior Art
Catalysts containing oxides of iron, bismuth and molybdenum, promoted with suitable elements, have long been used for the conversion of propylene and/or isobutylene at elevated temperatures in the presence of ammonia and oxygen (usually in the form of air) to manufacture acrylonitrile and/or methacrylonitrile. In particular, Great Britain Patent 1436475; U.S. Pat. Nos. 4,766,232; 4,377,534; 4,040,978; 4,168,246; 5,223,469 and 4,863,891 are each directed to bismuth-molybdenum-iron catalysts which may be promoted with the Group II elements to produce acrylonitrile. In addition, U.S. Pat. Nos. 5,093,299, 5212,137, 5,658,842 and 5,834,394 are directed to bismuth-molybdenum promoted catalysts exhibiting high yields to acrylonitrile.
In part, the instant invention relates to an attrition resistant supported bismuth-molybdenum-iron catalysts promoted with cerium. It has been discovered that by controlling the relative amounts of these iron and cerium impacts the hardness of the catalyst. Prior art catalysts were often characterized by low ratios of Ce to Fe (e.g. less than about 0.7) which tended to produce softer less attrition resistant catalysts even when combined with a support material.